The present invention relates to a rotary rolling piston compressor, and more specifically to a new implementation for the discharge system of this type of compressor.
The dimensioning of the discharge system components of a rotary rolling piston compressor, which are the discharge orifice, the discharge valve, the valve reinforcement and the bumper is crucial to the compressor's satisfactory performance.
Among the variables that influence this dimensioning is the discharge orifice diameter. A large diameter has the advantage of more rapidly discharging the gas compressed in the interior of the cylinder, therefore, reducing the loss by over compression, related to the readiness of the cylinder emptying at every discharge cycle. However, a discharge orifice of a large diameter increases the compressor dead volume. This impairs the compressor volumetric efficiency by the gas backflow at high pressure to the suction volume and it may reduce the suction fill up operation. Also the energy efficiency is decreased, also by the gas that flows from the dead volume back to the suction volume since this increases the compression work at every new cycle.
Another disadvantage of using a large diameter at the discharge orifice is due to the geometrical fact that the larger is the orifice the earlier the compressor compression cycle will finish, i.e., at a rotation angle some degrees earlier. This reduces the compression cycle and at the same time it also increases another dead volume which is formed between the cylinder and the rolling piston walls and the vane wall at the end of the compression, giving rise to the same disadvantages already said to be the case of the dead volume created in the discharge orifice. Besides that, a larger discharge orifice diameter increases the compressor noise level. This is described in the technical literature on the subject.
One method commonly used to reduce the above mentioned problems, especially in large capacity compressors, is the utilization of two discharge orifices and respective valves, each one placed at each end of the cover of the compressor set. This solution has the disadvantages of needing the placement of two discharge valves with all their assembly procedures and the machining of two valve seats, as well as requiring the provision of two muffler chambers. Furthermore, an increase of the compressor noise level is almost certain to happen.
Another known solution uses a discharge system with cylindrical valve (see Brazilian patent PI 860 3449). In this solution, the discharge area is enlarged with the placement of several holes lying across the cylinder internal wall. Although this solution is effective in relation to the efficiency of the gas discharge, obviously it is difficult to execute due to the transverse machining of the holes.